Wave energy converter (WEC) with magnetic braking

Abstract

A magnetic braking system for inhibiting excessive motion between a float and a column intended to be placed in a body of water; with the float and column moving relative to each other as a function of the waves present in the body of water. The braking system includes a permanent magnetic assembly (PMA) mounted on, and attached to, one of the float and column and a coil assembly (or a conductive plate) mounted on, and attached to, the other one of the float and column. The braking system is mounted such that motion between the float and the column is inhibited when the displacement of the float relative to the column exceeds a predetermined operating range.

1. A wave energy converter (WEC) with magnetic braking comprising:
 a float and a column intended to be placed in a body of water with the float and column moving relative to each other as a function of waves present in the body of water; 
 a permanent magnet assembly (PMA) mounted on one of the column and float and an induction coil assembly (ICA) mounted on the other one of the column and float for causing voltages to be generated across the induction coil assembly when the PMA and the ICA, mounted on the float and column move relative to each other within a given operating range, defining an active power generating range, whereby the relative movement of the float and column is converted into electrical energy; and 
 magnetic apparatus mounted above and below the induction coil assembly for inhibiting movement of the column relative to the float when the PMA moves above or below the ICA, outside the active power generating range. 
 
     
     
       2. A WEC as claimed in  claim 1 , wherein said magnetic apparatus includes a first electrically conductive metal plate, mounted above the ICA, for generating a magnetic field between the PMA and said first plate when the PMA is in close proximity to said first plate of a nature to inhibit movement of the float relative to the column beyond said operating range; and a second electrically conductive metal plate mounted below the ICA for generating a magnetic field between the PMA and said second plate when the PMA is in close proximity to said second plate of a nature to inhibit movement of the float relative to the column beyond said operating range. 
     
     
       3. A WEC as claimed in  claim 1 , wherein said magnetic apparatus includes a first braking coil assembly mounted above the ICA for generating a large magnetic field between the PMA and said first braking coil assembly of a nature to inhibit movement of the column relative to the float when the PMA is in close proximity to said first braking coil assembly; and a second braking coil assembly mounted below the ICA for generating a large magnetic field between the PMA and said second braking coil assembly of a nature to inhibit movement of the column relative to the float when the PMA is in close proximity to said second braking coil assembly. 
     
     
       4. A WEC as claimed in  claim 3  wherein a selectively enabled switch is connected across each braking coil assembly for selectively short circuiting the braking coil assembly across which the switch is connected. 
     
     
       5. A WEC as claimed in  claim 4  wherein said WEC includes means for sensing the position of at least one of the PMA and the ICA for controlling a turn-on and a turn-off of the selectively enabled switches connected across the braking coil assemblies. 
     
     
       6. A WEC as claimed in  claim 3  wherein each one of the first and second braking coil assembly is short circuited. 
     
     
       7. A WEC as claimed in  claim 1 , wherein said PMA is mounted on one of the column and float and the ICA is mounted on the other one of the column and float, and wherein the column can move up and down relative to the float. 
     
     
       8. A WEC as claimed in  claim 1  wherein the column is stationary and the float moves up and down relative to the column. 
     
     
       9. A WEC as claimed in  claim 1  wherein the column and the float can both move relative to each other. 
     
     
       10. A WEC as claimed in  claim 1  wherein the float is stationary and the column moves up and down relative to the float. 
     
     
       11. A wave energy converter (WEC) comprising:
 a float and a column intended to be placed in a body of water with the float and column moving relative to each other as a function of waves present in the body of water; 
 a permanent magnet assembly (PMA) attached to a section of the column and float and a first coil assembly attached to a first section of the other one of the column and float; said PMA and first coil assembly being magnetically coupled for causing voltages to be generated across the first coil assembly when the float and column move relative to each other within a given operating range; and 
 a second coil assembly mounted above the first section and a third coil assembly mounted below the first section of the other one of the column and float, said second and third coil assemblies interacting with the PMA so as to inhibit movement of the column relative to the float when the PMA moves above or below the first section, beyond said operating range. 
 
     
     
       12. A WEC as claimed in  claim 11 , wherein a first normally open switch is connected across the second coil assembly and wherein the switch is selectively closed for applying a short circuit across the second coil assembly when the PMA moves so as to be near the second coil assembly; and wherein a second normally open switch is connected across the third coil assembly and wherein the switch is selectively closed for applying a short circuit across the third coil assembly when the PMA moves so as to be near the third coil assembly. 
     
     
       13. A WEC as claimed in  claim 12 , wherein the PMA is mounted on the column and the coil assemblies are mounted on the float. 
     
     
       14. A WEC as claimed in  claim 12 , wherein the PMA is mounted on the float and the coil assemblies are mounted on the column. 
     
     
       15. A combination comprising
 a float and a column intended to move relative to each other as a function of external forces applied to them; 
 a power take off device (PTO) connected between the float and the column responsive to the movement between the float and the column for converting their relative motion to electrical energy so long as they move within an operating range; and 
 means for limiting the relative motion between the float and column outside the operating range, said limiting means including a permanent magnetic assembly (PMA) attached to one of the column and float and a braking coil assembly (BCA) attached to the other one of the column and float for causing voltages to be generated across the BCA when the PMA and the BCA are in close proximity such that electromagnetic forces are generated opposing motion of the float relative to the column outside of the operating range. 
 
     
     
       16. The combination as claimed in  claim 15  wherein the PTO is a linear electric generator.